Displaying publications 81 - 89 of 89 in total

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  1. Ng SS, Hutubessy R, Chaiyakunapruk N
    Vaccine, 2018 05 03;36(19):2529-2544.
    PMID: 29625764 DOI: 10.1016/j.vaccine.2018.03.024
    BACKGROUND: The success of human papillomavirus (HPV) national immunization program depends on effective strategies in optimizing the uptake of HPV vaccine. Given the increasing number of economic evaluations, this review was conducted to update the economic evidence on HPV vaccination, by focusing on: (i) 9-valent vaccine compared to bi- or quadrivalent vaccine; (ii) gender-neutral vaccination compared to female only vaccination; and (iii) multiple age cohort immunization compared to single age cohort immunization.

    METHODS: Searches were performed until June 2016 using 4 databases: PubMed; Embase; Cochrane Library; and LILACS. The combined WHO, Drummond and CHEERS checklist were used to evaluate the quality of included studies.

    RESULTS: Thirty-four studies were included in the review and most of them were conducted in high-income countries. The inclusion of adolescent boys in vaccination program was found to be cost-effective if vaccine price and coverage was low. When coverage for female was above 75%, gender-neutral vaccination was less cost-effective than when targeting only girls aged 9-18 years. Current evidence does not show conclusive proof of greater cost-effectiveness of 9-valent vaccine compared to the older HPV vaccines as the price for 9-valent vaccine was still uncertain. Multicohort immunization strategy was cost-effective in the age range 9-14 years but the upper age limit at which vaccination was no longer cost-effective needs to be further investigated. Key influential parameters identified were duration of vaccine protection, vaccine price, coverage, and discounting rates.

    CONCLUSIONS: These findings are expected to support policy-makers in making recommendations for HPV immunization programs on either switching to the 9-valent vaccine or inclusion of adolescent boys' vaccination or extending the age of vaccination.

  2. Hassan Raza S, Yousaf M, Zaman U, Waheed Khan S, Core R, Malik A
    Vaccine, 2023 Mar 03;41(10):1703-1715.
    PMID: 36754765 DOI: 10.1016/j.vaccine.2023.01.047
    Guarding against an anti-science camouflage within infodemics is paramount for sustaining the global vaccination drive. Vaccine hesitancy remains a growing concern and a significant threat to public health, especially in developing countries. Infodemics, conspiracy beliefs and religious fatalism primarily fuel vaccine hesitancy. In addition, anti-vaccine disinformation, lack of understanding, and erroneous religious beliefs also trigger vaccine hesitancy. Global behavioral strategies such as wearing face masks and long-term preventive measures (i.e., COVID-19 vaccination) have effectively limited the virus's spread. Despite the alarming rate of global deaths (i.e., over 99% being unvaccinated), a large proportion of the global population remains reluctant to vaccinate. New evidence validates the usefulness of technology-driven communication strategies (i.e., digital interventions) to address the complex socio-psychological influence of the pandemic. Hence, the present research explored the digital information processing model to assess the interface between informational support (through digital interventions) and antecedents of vaccine hesitancy. This research involved two separate studies: a focus group to operationalize the construct of infodemics, which remained ambiguous in previous literature (Study 1), followed by a cross-sectional survey (Study 2) to examine the conceptual model. Data were collected from 1906 respondents through a standard questionnaire administered online. The focus group's findings revealed a multi-dimensional nature of infodemics that was also validated in Study 2. The cross-sectional survey results substantiated infodemics, religious fatalism and conspiracy beliefs as significant predictors of vaccine hesitancy. Similarly, conspiracy beliefs negatively influence an individual's psychological well-being. Furthermore, information support (through digital intervention) affected infodemics and religious fatalism, whereas it inversely influenced the strength of their relationships with vaccine hesitancy. Information support (through digital intervention) also moderated the relationship between conspiracy beliefs and psychological well-being.
  3. Ozawa S, Wonodi C, Babalola O, Ismail T, Bridges J
    Vaccine, 2017 11 07;35(47):6429-6437.
    PMID: 29037575 DOI: 10.1016/j.vaccine.2017.09.079
    BACKGROUND: Understanding and ranking the reasons for low vaccination uptake among parents in northern Nigeria is critical to implement effective policies to save lives and prevent illnesses. This study applies best-worst scaling (BWS) to rank various factors affecting parents' demand for routine childhood immunization.

    METHODS: We conducted a household survey in Nahuche, Zamfara State in northern Nigeria. Nearly two hundred parents with children under age five were asked about their views on 16 factors using a BWS technique. These factors focused on known attributes that influence the demand for childhood immunization, which were identified from a literature review and reviewed by a local advisory board. The survey systematically presented parents with subsets of six factors and asked them to choose which they think are the most and least important in decisions to vaccinate children. We used a sequential best-worst analysis with conditional logistic regression to rank factors.

    RESULTS: The perception that vaccinating a child makes one a good parent was the most important motivation for parents in northern Nigeria to vaccinate children. Statements related to trust and social norms were ranked higher in importance compared to those that highlighted perceived benefits and risks, healthcare service, vaccine information, or opportunity costs. Fathers ranked trust in the media and views of their leaders to be of greatest importance, whereas mothers placed greater importance on social perceptions and norms. Parents of children without routine immunization ranked their trust in local leaders about vaccines higher in considerations, and the media's views lower, compared to parents with children who received routine immunization.

    CONCLUSIONS: Framing immunization messages in the context of good parenting and hearing these messages from trusted information sources may motivate parental uptake of childhood vaccines. These results are useful to policymakers to prioritize resources in order to increase awareness and demand for childhood immunization.

  4. Loh FK, Nathan S, Chow SC, Fang CM
    Vaccine, 2019 07 09;37(30):3989-4000.
    PMID: 31186188 DOI: 10.1016/j.vaccine.2019.05.083
    Since the discovery of Toxoplasma gondii in 1908, it is estimated that one-third of the global population has been exposed to this ubiquitous intracellular protozoan. The complex life cycle of T. gondii has enabled itself to overcome stress and transmit easily within a broad host range thus achieving a high seroprevalence worldwide. To date, toxoplasmosis remains one of the most prevalent HIV-associated opportunistic central nervous system infections. This review presents a comprehensive overview of different vaccination approaches ranging from traditional inactivated whole-T. gondii vaccines to the popular DNA vaccines. Extensive discussions are made to highlight the challenges in constructing these vaccines, selecting adjuvants as well as delivery methods, immunisation approaches and developing study models. Herein we also deliberate over the latest and promising enhancement strategies that can address the limitations in developing an effective T. gondii prophylactic vaccine.
  5. Richardson A, Morris DE, Clarke SC
    Vaccine, 2014 Jul 16;32(33):4119-23.
    PMID: 24907487 DOI: 10.1016/j.vaccine.2014.05.062
    Streptococcus pneumoniae, Haemophilus influenzae type b and Neisseria meningitidis are leading causes of vaccine-preventable diseases such as meningitis, sepsis and pneumonia. Although there has been much progress in the introduction of vaccines against these pathogens, access to vaccines remains elusive in some countries. This review highlights the current S. pneumoniae, H. influenzae type b, and N. meningitidis immunization schedules in the 10 countries belonging to the Association of Southeast Asian Nations (ASEAN). Epidemiologic studies may be useful for informing vaccine policy in these countries, particularly when determining the cost-effectiveness of introducing new vaccines.
  6. Lee MHP, Tan CW, Tee HK, Ong KC, Sam IC, Chan YF
    Vaccine, 2021 03 19;39(12):1708-1720.
    PMID: 33640144 DOI: 10.1016/j.vaccine.2021.02.024
    Enterovirus A71 (EV-A71) causes hand, foot and mouth disease (HFMD) in young children. It is associated with severe neurological complications and death. This study aims to develop a live-attenuated vaccine by codon deoptimization (CD) and codon-pair deoptimization (CPD) of EV-A71. CD is generated by introducing the least preferred codons for amino acids while CPD increases the presence of underrepresented codon pairs in the specific genes. CD and CPD chimeras were generated by synonymous mutations at the VP2, VP3, VP1 and 2A gene regions, designated as XYZ. All twelve deoptimized viruses were viable with similar replication kinetics, but the plaque sizes were inversely proportional to the level of deoptimization. All the deoptimized viruses showed attenuated growth in vitro with reduced viral protein expression at 48 h and lower viral RNA at 39 °C. Six-week-old ICR mice were immunized intraperitoneally with selected CD and CPD X and XY vaccine candidates covering the VP2-VP3 and VP2-VP3-VP1 genes, respectively. All vaccine candidates elicited high anti-EV-A71 IgG levels similar to wild-type (WT) EV-A71. The CD X and CPD X vaccines produced robust neutralizing antibodies but not the CD XY and CPD XY. On lethal challenge, offspring of mice immunized with WT, CD X and CPD X were fully protected, but the CD XY- and CPD XY-vaccinated mice had delayed symptoms and eventually died. Similarly, active immunization of 1-day-old suckling mice with CD X, CPD X and CD XY vaccine candidates provided complete immune protection but CPD XY only protected 40% of the challenged mice. Histology of the muscles from CD X- and CPD X-vaccinated mice showed minimal pathology compared to extensive inflammation in the post-challenged mock-vaccinated mice. Overall, we demonstrated that the CD X and CPD X elicited good neutralizing antibodies, conferred immune protection and are promising live-attenuated vaccine candidates for EV-A71.
  7. Chooi WH, Ng PW, Hussain Z, Ming LC, Ibrahim B, Koh D
    Vaccine, 2022 Mar 15;40(12):1699-1701.
    PMID: 35210120 DOI: 10.1016/j.vaccine.2022.02.034
  8. Mohd Azizi FS, Kew Y, Moy FM
    Vaccine, 2017 05 19;35(22):2955-2961.
    PMID: 28434687 DOI: 10.1016/j.vaccine.2017.04.010
    BACKGROUND: Vaccine hesitancy is a threat in combating vaccine-preventable diseases. It has been studied extensively in the Western countries but not so among Asian countries.

    OBJECTIVES: To assess the test-retest reliability of the Parent Attitudes about Childhood Vaccines (PACV) questionnaire in Malay language; to determine the prevalence of vaccine hesitancy among parents and its associations with parents' socio-demographic characteristics.

    METHODS: Forward and backward translation of PACV in Malay language was carried out. The reliability of the Malay-PACV questionnaire was tested among parents with children. The same questionnaire was used to study vaccine hesitancy among parents in a tertiary hospital in Kuala Lumpur. Information pertaining to socio-demographic characteristics, sources of information regarding vaccination and vaccine hesitancy were collected. Associations between vaccine hesitancy with socio-demographic factors were tested using Multivariable Logistic Regression.

    RESULTS: The Spearman correlation coefficient and Cronbach alpha for total PACV was 0.79 (p<0.001) and 0.79 respectively. The intra-class correlation coefficients of the subscales ranged from 0.54 to 0.90 demonstrating fair to excellent reliability. A total of 63 (11.6%) parents were noted to be vaccine hesitant. In the univariate analyses, vaccine hesitancy was associated with unemployed parents, parents who were younger, had fewer children and non-Muslim. In the multivariate model, pregnant mothers expecting their first child were four times more likely to be vaccine hesitant compared to those who already had one or more children (aOR: 3.91, 95% CI: 1.74-8.79) and unemployed parents were also more likely to be vaccine hesitant (aOR: 1.97, 95% CI: 1.08-3.59). The internet (65.6%) was the main source of information on vaccination followed by brochures (56.9%).

    CONCLUSION: The Malay-PACV questionnaire is reliable to be used. The prevalence of vaccine hesitancy among the multi-ethnic Malaysians was comparable with other populations. Pregnant mothers expecting their first child and unemployed parents were found to be more vaccine hesitant.

  9. Kalok A, Loh SYE, Chew KT, Abdul Aziz NH, Shah SA, Ahmad S, et al.
    Vaccine, 2020 02 24;38(9):2183-2189.
    PMID: 32001070 DOI: 10.1016/j.vaccine.2020.01.043
    BACKGROUND: Vaccine hesitancy is a complex behaviour which involves various degrees of indecision about specific vaccines or vaccination uptake. Access to antenatal care had been associated with positive vaccine behavior.

    OBJECTIVE: To determine the prevalence of vaccine hesitancy towards childhood immunisation amongst urban pregnant mothers and the associated socio-demographic factors.

    METHODS: A cross-sectional study was conducted among 1081 women who received antenatal care at a teaching hospital in Kuala Lumpur. Vaccine hesitancy was assessed using the Parent Attitudes about Childhood Vaccines (PACV) Survey in both English and validated Malay versions. The sociodemographic data of the mothers and their partners, source of vaccine information and reasons for hesitancy were analysed.

    RESULTS: Eighty-six (8.0%) pregnant mothers were vaccine hesitant. Ethnicity, religion, number of children, educational level and employment status were significantly associated with vaccine hesitancy. Multivariable analysis showed that a low level of education was the most significant risk factor (p 

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